Generally, exterior masonry wall surfaces for buildings are constructed in conjunction with a structural inner wall which serves as the main supporting wall. Such inner structural wall is usually comprised of either (1) a frame wall (wood or steel studs, with an inner surface of drywall or some interior finish) or (2) concrete blocks, placed together to form such inner wall, and spaced apart from the exterior masonry wall, or (3) a concrete shear wall, in a wall construction technique commonly known as cavity wall construction Between the exterior masonry wall, and the inner structural wall there generally exists an air space, which insulation may partially fill.
In rain screen construction, weep-hole ventilators (porous blocks) are located in spaced intervals along the lower masonry row of each floor level of an exterior masonry wall, allowing air communication from the exterior to the interior cavity. These weep-hole ventilators serve a dual purpose. Firstly, such weep-hole ventilators serve to equalize the air pressure on both sides of the masonry wall (i.e. the exterior and interior masonry wall surfaces) by allowing air to pass therethrough to equalize the air pressure in the cavity and the exterior. Secondly, weep hole ventilators allow moisture which may have condensed on the inner masonry wall surface, and trickled down to the lower brick row level, to flow through such ventilators to the outside of the masonry wall. This prevents entrapment of moisture in the cavity immediately adjacent the inner wall surface of the exterior masonry wall, and further serves to prevent moisture permeation of the insulation located in the cavity adjacent the inner structural wall.
Should, however, moisture be allowed to remain on the inner wall surface of the exterior masonry wall, (i.e. in the interior cavity) it may seep to the exterior surface of the masonry wall from the interior wall surface thereof through the masonry bricks comprising the masonry wall. This is very undesirable, since the evaporating moisture from the exterior surface of the brick leaves deposited minerals thereon, causing the common unsightly "whitening" of the exterior masonry wall surface in a process called efflorescence.
Also, should moisture be allowed to remain in the cavity, and continue to seep through the masonry wall from the interior to the exterior, such moisture may at some point freeze, causing cracks in the masonry wall due to the force of expansion of the frozen moisture. This is also very undesirable.
The problems of efflorescence, moisture seepage through the masonry wall, and frost cracking, have commonly been overcome by proper ventilation of the cavity by use of a plurality of weep hole ventilators along the bottom row surface of the masonry wall.
Frequently, however, during construction of such masonry walls, excess mortar used in cementing masonry bricks one to another is extruded from between such mortar joints, and falls within the cavity space to the lower brick row level, where the weep-hole ventilators are located. Any excess mortar on the exterior surface side of the brick wall may easily be removed. However, in cavity wall construction or composite wall construction, excess mortar piles up at the base of the masonry wall in the interior cavity, intermediate the outer and inner walls, where the weep-hole ventilators are located, causing the weep-hole ventilators to become plugged.
This situation is highly undesirable, for the reasons mentioned above, but also for the further reason that moisture may begin to accumulate at the bottom of the cavity, being unable to escape to the exterior because of the plugged weep-hole ventilators. Although galvanized metal flashing is usually provided along the bottom surface of the outer masonry wall, accumulated moisture may then seep through seams in such flashing and through the insulation, and into the inner structural wall. For obvious reasons, this is also undesirable.
Building contractors and architects have recognized this problem, and some techniques have been used to attempt to deal with such problem.
One such early method involved placing a removable trowel, or mortar-collecting device, along the bottom row on the interior side of the masonry wall under construction, to which ropes were attached. During construction of the masonry wall, any extruded mortar fell onto the mortar-collecting device. Upon construction of the wall, the device containing extruded mortar was pulled up from the interior cavity by means of the ropes, and the excess mortar was thereby removed.
Recently, however, building codes require that re-inforcing material having closed loop protrusions, or reinforcing ties which extend intermediate the inner and outer wall surfaces at spaced intervals be provided to allow the outer masonry wall to thereby be "tied" to the interior structural wall. This re-inforcing material may have inwardly protruding ties, frequently in the form of closed loop stirrup members and commonly 3/16" diameter steel wire, which thereby prevent the trowel from being removed from the interior cavity, since the inwardly protruding "ties" prevent the trowel from being pulled upward by the ropes and thereby from being removed from the cavity.
Another practice employed in the industry involves use of a series of corrugated water-resistant material placed adjacent the inner wall surface of the masonry wall, and overlying such surface. These corrugated overlying materials are placed between horizontal rows of protruding closed loop stirrup members along the wall and are pressed against such surface usually by insulation within the inner cavity.
Such horizontally corrugated overlying materials are partially effective in preventing excess extruded mortar from falling to the base level row of bricks, and thus prevent plugging of the weep hole ventilators. However, the primary purposes of such devices is to increase the insulation capability of the wall by trapping air pockets along the horizontal corrugations, and provide a waterproof barrier to prevent insulation from contacting a moist inner wall surface of the masonry wall, upon which moisture may have condensed. Such horizontal corrugations pose a problem, however, in that they also prevent moisture which condenses on the interior wall surface from trickling downwardly to the weep-hole ventilators. This allows the moisture to collect in the horizontal corrugations, and the problem of moisture seepage to the exterior masonry wall surface, and the problems of efflorescence and frost cracking, described above, are not overcome. Moreover, the quantity of material necessary to cover the inner wall surface requires costly expenditure in terms of material.